An example of a discharge lamp igniting apparatus is disclosed in Japanese Patent Application Publication JP2004-311199A. According to the technology disclosed in this publication, abnormal arcing of a discharge lamp is detected on the basis of a current flowing through the lamp and a voltage applied to the lamp.
According to the above-cited publication, it is abnormal arcing that is detected. However, a possible different technique can be thought of. According to such different technique, the technique of detecting a current through the discharge lamp disclosed in this publication is used to determine that abnormality has been detected when the current flowing through the discharge lamp decreases below a predetermined reference current, and the power supply to the discharge lamp is interrupted to thereby turn off the lamp. When the lamp's operation is unstable in the initial operating state, the current flowing through the lamp is below the predetermined reference current. According to this technique, such state could be judged to be an abnormal state although the discharge lamp has not been turned on yet, to thereby undesirably disrupt the supply of power to the lamp. Then, according to this technique, it would be very frequent that the lamp is not turned on.
An object of the present invention is to provide a discharge lamp igniting apparatus with reduced ignition failures.